1. Field of the Invention
The present invention relates to a process for preparing a gas absorbent which can absorb ethylene gas and the like, particularly to a process for preparing a gas absorbent which comprises active carbon treated with sodium bromate and has improved gas absorbency.
2. Description of the Prior Art
Up to now, normal active carbon and active carbon treated with water have been generally known as absorbents able to absorb and remove gases of every kind. However, when used as an absorbent, the absorbency of these active carbons reaches a limit in a short period because the active carbon absorbs water and the like together with ethylene. As a result, they cannot sufficiently absorb ethylene and the ethylene gas which has been absorbed escapes from them together with water.
Many improvements have been proposed toward overcoming the problems of the aforesaid active carbons as disclosed, for example, in Japanese Patent Publication No. 7339/1973, Japanese Patent Laid-Open Publication No. 117060/1979, Japanese Patent Laid-Open Publication No. 138146/1979 and Japanese Patent Publication No. 39149/1982, but no absorbent having sufficient physical properties has been realized yet.
On the other hand, the present inventors previously proposed an active carbon treated with potassium bromate as "a reagent for preserving freshness of vegetables" (Japanese Patent Laid-Open Publication No. 88752/1981) and "a gas absorbent and preparing method thereof" (Japanese Patent Laid-Open Publication No. 98141/1983). The aforesaid publication disclose absorbents with selective absorbency which do not suffer degradation of absorbency in the presence of steam and carbon dioxide.
Even though said absorbents have superior properties compared with the earlier active carbons, they at the same time have the following problems:
(a) the active carbon has to be treated in a treating solution at an elevated temperature because of the low solubility of potassium bromate. PA1 (b) unless the temperature of the treating solution is kept high, the concentration of potassium bromate falls and, as a result, the ethylene removing ability of the absorbent obtained is weakened. PA1 (c) gas which seems to be bromine is produced at elevated temperatures and impairs the working environment wrong, and, therefore special equipment for maintaining a proper working environment has to be provided. PA1 (d) preparation of a high quality absorbent is thus not easy.